Fiberglassing a Rocket

Back in April 2011 myself and a friend bought a Forte Rocket kit from Apogee Rockets to complete my level one and two NAR certification flight. The kit used standard cardboard tubing and through wall fins. After spending the time putting the kit together, I decided to go the extra mile and fiberglass the rocket. I’m writing this to give a quick tutorial on fiberglassing rockets and tell you about the lessons that I learned from the experience.

Once I had the rocket completed I decided to go to Autozone and but some of the fiberglass. I bought:

  • 3m fiberglass cloth (8 square ft/.75 square m) $10
  • 3m fiberglass resin (32 oz/1 liter) $22.50

Knowing how much fiberglass cloth and resin you need is a challenge. I bought 8 square feet for my rocket, which was just enough to double layer the 3.5 ft tall cardboard tube and fin section of the rocket. I only ended up using about 60% of the 32 oz resin.

To apply the fiberglass, I used some good quality rubber gloves, foam paint brushes, and an object for squeegeeing the resin. The foam brushes did dissolve in the resin and sometimes left little bits and pieces behind. If you have an old paint brush you don’t mind throwing away it would be a better application tool. For the gloves, I suggest getting the good quality rubber gloves. The fiberglass resin will eat through latex gloves and many of the other thin gloves. If you are careful with the rubber gloves and don’t allow the fingers to cure together, then they will be in good condition after use with the exception of small area of resin hardened on the outside. For the squeegee, I used an old plastic card as a squeegee. It worked great.

When you mix the resin I suggest using a cheap glass cup. I originally used wax dixie cups, but the resin ate through them (probably because of the heat). Keep in mind that as the resin cures it gets hot. Mix enough resin to complete the fiberglass sheet you are working on.

Be sure that the area you are working in is well shielded with cardboard. If a drop of resin fall on a concrete floor and cures, it will be there for the eternity of time. Also wear pants and a long sleeve shit that you don’t care about. The resin will get on your clothes.

To allow the resin to cure faster you may be interested in using a heater. The resin usually takes 24 hours to completely cure, but by using a heater you can get that number down to around 6 hours.

If you plan on sanding the fiberglass I suggest using hefty gloves, a hospital style facemask, and safety glasses that cover your eyes well. Even with this protection you will still get fiberglass splinters. The best way to minimise the exposure is to make sure you do a good job with the application of the resin and making sure that your fiberglass cloth is cut perfectly to size. I suggest just using sandpaper sheets. For a perfectly smooth finish I recommend using a 120 grit followed by a 600 grit followed by a high grit. Be prepared to use a lot of the high grit sandpaper, fiberglass has a way with clogging the grits up.

To apply the fiberglass:

  1. Measure the area over which you want to fiber glass. Add approximately 2 inches (4 cm) overhang on each side because when you cut the cloth you will effectively loose when you cut the section out
  2. Place a piece of the cloth on the rocket to make sure that it is the right size
  3. Mix the resin with the hardener in the glass cup
  4. Apply generous amounts of resin to the cloth
  5. Use the squeegee to eliminate all air pockets and excess resin
  6. You can use a rag to wipe off the pools of resin as long as the resin is not close to curing
  7. Repeat the process for each piece

Here’s some pictures of my finished product.

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